1. Field of the Invention
This invention relates to farm implement actuators in general and in particular to a linkage system for simultaneously actuating a plurality of farm implements drawn by the same vehicle.
2. Description of the Prior Art
U.S. Pat. No. 2,344,326 discloses a mechanism for actuating working tools mounted on a tractor. Fluid-extensible devices are connected to the tractor for moving the tools to predetermined positions with respect to the tractor when retracted and when in the working position. A manually adjustable means adapted to react against the tractor and connected to a sleeve element surrounding the fluid-extensible device and slidable with respect thereto serves as a stop against which one of the extensible parts of the fluid-extensible device will abut as the fluid-extensible device is collapsed to place the working tools in their ground working position. The sleeve element can be adjusted in position to change the ground-working depth of the tools.
U.S. Pat. No. 2,417,580 discloses a potato digger with a lifting clutch mechanism for raising and lowering the operating means between ground engaging and transport positions. A pair of digging implements are connected in side by side relation and each includes a vertically adjustable shovel unit, elevator chain means supported on the shovel unit and the rear portion of the implement, a shaft supported on one of the implements and connected to drive the elevator chain means of both implements, means for driving the shaft, a power lift mechanism on one implement and operably connected to be driven by the shaft, and connections between the power lift mechanism and each of the shovel units whereby actuation of the power lift mechanism raises or lowers both shovel units.
U.S. Pat. No. 2,496,760 discloses a grading apparatus which includes a blade having a working height adjustment. The blade is connected to a pivoted beam. The beam is raised and lowered through a linkage including a threaded rod and bushing with a stop nut to determine the position of the blade as it is raised and lowered.
U.S. Pat. No. 2,617,342 discloses a lift mechanism for a farm implement that functions as a depth gauge in the operation of the implement and at the same time permits the implement to raise over objects. A lifting bar is attached to the frames of tools by chains which allow up and down movement of the tools but limit the depth of the tools. An adjustable set screw is utilized to determine the angle of the lifting bar with respect to the portion of the draw bar attached to the tractor.
U.S. Pat. No. 2,648,997 discloses an adjustable top link for a three point implement mounting linkage for adjusting the position of farm implements. The top link comprises a tubular member having longitudinally adjustable screw members projecting out of each end which threadably engage a pair of nut members contained in the tube. Each screw member the corresponding nut are oppositely threaded so that such screws may be moved inwardly or outwardly merely by rotating the tube portion. Each screw member includes a yoke for attachment to hitch points on the tractor and implement. A locking member prevents movement of the tube when the desired adjustment has been made.
U.S. Pat. No. 2,741,173 discloses a tiller implement frame wherein the rotary tiller units may be vertically adjusted in unison to a selected working depth without materially altering the working position of the rotary tillers relative to a horizontal plane. A hydraulic cylinder acts upon a lever arm which raises and lowers the rotary tillers. When the cylinder is extended, the tool is raised. When the cylinder is retracted, the tool is lowered with the lower depth being limited by a piston stop screw threaded axially into the cylinder at its forward end. The mechanism also includes a turnbuckle for varying the position of the mounting frame containing the tool relative to the horizontal plane.
U.S. Pat. No. 2,886,116 discloses a rotary cultivating apparatus. An implement frame is pivotally mounted on a carriage. A telescopic member including a cylinder having a trunnion connection to the implement frame contains a non-rotatable nut working on a screw threaded portion of a rod which extends through a trunnion block supported by a stanchion for determining the working depth of the implement. A compression spring reacts between the nut and the end of the cylinder. A hydraulic ram cylinder has one end pivoted from the stanchion and its piston rod pivotally connected to the implement for raising and lowering the implement.
U.S. Pat. No. 2,869,656 discloses a control mechanism for a tillage tool known as a middle buster. The height of the tool is determined by a connection to a ground-engaging gauge wheel by means of an eye-bolt pivotally connected at one end to the tool and slidably received in a swivel at the other end. The bolt is threaded for receiving a pair of nuts, one on each side of the swivel for adjusting the depth of the tool.
U.S. Pat. No. 3,547,203 discloses a back blade assembly utilizing a hydraulic cylinder to raise and lower a blade. Spring biased supports are provided to allow the blade to pivot about a pivot point when it strikes a ground protuberance. Threaded adjustments determine the amount of rotational movement of the blade for a given force.